The present invention generally relates to radiocommunication systems and methods for signalling in radiocommunication systems and, more particularly, to systems and methods for communicating multimedia attachments to short text messages in radiocommunication systems.
The GSM describes a European standard for radiocommunication and the corresponding Public Land Mobile Network (PLMN) which is intended to provide uniformity so that users can access radiocommunication systems throughout Europe with minimal equipment compatibility problems. The GSM includes many services for subscribers, including a message function service called the Short Message Service (SMS) which provides for the transmission of messages having up to 160 alphanumeric characters to be sent to a subscriber at his or her mobile unit.
Unlike voice or data connections supported in radiocommunication systems, SMS messages are typically transmitted as overhead signalling, e.g., as part of the information provided on control channels. Thus, SMS service is more similar in many ways to conventional paging functions than to wireless voice or data connections, but also has several differences. For example, if a phone is switched off, or otherwise unreachable, the SMS message is stored and can later be sent to the designated subscriber when that subscriber is reconnected to the system. The SMS message originates from either a mobile unit, which transmits the SMS message to a service center, or from a user external to the radiocommunication system, e.g., by calling an operator at a service center who enters the SMS message into the radiocommunication system.
When an SMS message is delivered from a service center to a mobile unit, regardless of how it originates, such a message is conventionally referred to as a “mobile terminated short message” (MTSM). If an SMS message originates at a mobile unit, the signal to the service center requesting forwarding of the SMS message is conventionally referred to as a “mobile originated short message” (MOSM). The conventional protocol for transmission of MTSMs is well established in the GSM, for example in the document entitled “GSM 09.02-Version 2” published in June 1992 which is incorporated here by reference and is described in more detail below with respect to FIG. 1.
Therein, an originating mobile station (MS-A) 2 sends an MOSM to the mobile switching center (MSC) 4 supporting the geographical area which the mobile station is currently visiting. Not shown explicitly in FIG. 1, but as will be apparent to those skilled in the art, is the base station which receives the signal from the mobile station 2 and forwards same to the MSC 4. The MSC 4 forwards the MOSM to interworking mobile switching center (IWMSC) 6 using an address of the service center assigned to, mobile station 2 as part of the overhead information associated with the MOSM.
The IWMSC provides centralized interfacing functionality for SMS messaging. For MOSMs, the IWMSC 6 operates to transfer short messages to an identified service center (SC). The IWMSC also functions to transfer results associated with SMS message transmission back to the MSC. Thus, in this example, IWMSC 6 forwards the MOSM to SC-A 8. SC-A 8 acknowledges receipt of the MOSM back to IWMSC 6, which in turn forwards an acknowledgement back to MSC 4.
Service centers are “store and forward” devices which are logically outside of the mobile radio network. SCs operate to receive and store SMS messages, deliver SMS messages to mobile stations (or receivers outside of the mobile network) and, optionally, customize delivery of SMS messages according to service profiles stored at the SC. In the current example, SC-A 8 receives the MOSM from the IWMSC 6 and, assuming for the sake of this example that the subscriber associated with MS-A has a service profile stored at SC-A 8, performs one or more operations to the MOSM in accordance with the service profile. These operations may include, for example, copying the received SMS message and storing same, sending the SMS message according to a distribution list defined by subscriber A, or converting the SMS message to a desired delivery media (e.g., a fax). After performing whatever operations are indicated by the service profile, SC-A 8 then sends the MOSM as an MTSM to the recipient identified in the MOSM. This occurs as follows.
The MTSM is first sent to an SMS-gateway mobile switching center (GMSC) 10. Like its counterpart the IWMSC, the GMSC acts as a port into the mobile radio network. Before the GMSC 10 can deliver the SMS message through the chain of nodes to the base station (not shown) which is serving the recipient's mobile station, the GMSC 10 must first determine the location of the recipient's mobile station (i.e., which MSC is currently serving that mobile station). Thus, GMSC 10 first interrogates the recipient's home location register (HLR) 12 to obtain routing information for the message.
HLRs store data relating to subscribers including, for example, current location of the subscribers' equipment, directory number (MSISDN), radio number plan identification (e.g., International Mobile Subscriber Identity (IMSI)), supplementary service profiles and teleservice profiles. For MTSMs, HLRs provide (upon request) the identity of the visited MSC associated with a recipient of the SMS message, as well as information relating to whether the mobile station can receive the message (e.g., whether the subscriber is barred from receiving MTSMs). In the current example, to interrogate the HLR 12, a GSM MAP message called “Send Routing Information for Short Message” is sent by the GMSC 10 to the HLR 12. The appropriate HLR for interrogation can be determined using the recipient's MSISDN, e.g., by translating the MSISDN into a CCITT No. 7 address.
After receiving the routing information, e.g., the visited MSC number and IMSI, from HLR 12, the GMSC 10 forwards the message to the visited MSC/VLR 14 which is currently serving the recipient's mobile station MS-B 16. Note that for purposes of simplicity the visitor location register (VLR) has been illustrated in FIG. 1 as being integrated with the mobile switching center, although in practice these two nodes can be physically separated. The VLR manages data associated with subscribers which are currently situated within its area of responsibility, e.g., those which have roamed into the service area of that VLR, the VLR being updated with information from a subscriber's home location register. With respect to handling SMS messages, the VLR also stores an indication if a mobile station is unreachable for delivery of a particular MTSM. The VLR notifies the HLR when a mobile station can later be reached to deliver the MTSM.
With the advent of the Internet, e-mail having multimedia attachments is a service that is growing in popularity with consumers. Today, although the SMS techniques described above provide functionality which is comparable to the text messaging attribute of e-mail, there exists no mechanism which would permit transmission or reception of an attached file, e.g., image files or audio files, by a remote, wireless terminal.
One solution to this problem would be to implement e-mail client software in each remote, wireless terminal, so that these devices could be used to send and receive e-mail much like a computer terminal. However, this would require adaptation of the air interface (i.e., the standardized interfaces which specify how information is transmitted between a base station and a mobile station in radiocommunication systems) and other additional complexity. Moreover, there are today many different e-mail standards, e.g., IMAP4 and POP3, each of which would require support to provide a similar type of service in the wireless environment.
From the foregoing, it is apparent that it would be desirable to modify conventional techniques for delivering SMS messages to provide an opportunity for attaching files, e.g., image, audio, etc., thereto. However, for the various reasons discussed above, it would be also desirable to provide this capability without introducing the complexity of turning wireless communication devices into e-mail clients per se.